It's a mess up there. Earth orbit is crowded with not only working satellites but also defunct orbiters, pieces of old rockets, and other miscellany. How will we clean up the refuse of the Space Age?

It's a mess up there. Earth orbit is crowded with not only working satellites but also defunct orbiters, pieces of old rockets, and other miscellany. How will we clean up the refuse of the Space Age?

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5 High-Tech Space-Junk Solutions

Since humans began launching things out of the stratosphere 60 years ago, we've littered the area around our planet with spent rockets and nonworking satellites. Now about 22,000 large pieces of trash circle the globe at thousands of miles per hour, posing a serious threat to functioning satellites and spacecraft and occasionally sending the astronaut inhabitants of the International Space Station running for cover.

Now and then—once every five years on average—hunks of junk smash into each other. When an abandoned Russian spacecraft hit the U.S. satellite Iridium-33 in 2009, the explosion created at least 1000 new pieces of space junk. Traveling at 17,500 miles per hour, even a paint chip can blow a hole through a spacecraft. And as more collisions create more pieces of garbage, the problem grows exponentially.

"We've got to stop that from happening, or it could become so unsafe in low Earth orbit that we wouldn't be able to go up there anymore," says Jerome Pearson, president of Star Technology and Research, which is developing its own methods of cleaning up space junk. "Right now, we have enough time to deal with this problem, but we need to start removing those big objects so they can't create more little pieces."

No nation yet has a concrete plan for an orbital cleanup. But some scientists are beginning to think seriously about what it would take. The Swiss Space Center at the Ecole Polytechnique Federale de Lausanne (EPFL), for example, recently announced that within the next five years it plans to launch a janitor satellite into space to grab an aging satellite and pull it to a fiery death in the Earth's atmosphere. "We are not going to change the problem of orbital debris by picking up one piece of debris," says Volker Gass, who helped to design the new CleanSpace One device. "But if you clean up a Coke can from your yard, you are setting an example, and maybe your neighbors will keep their yards clean too."

Right now NASA is exploring different strategies for cleaning up both large and small junk. Some scientists at the agency are advocating that humans start cleaning up orbital space by 2020—if we remove five to 10 pieces of junk per year, they say, then orbital debris will remain at manageable levels for centuries. "We want to move forward as many different technologies as we can, in hopes that one will shine," NASA chief technologist Mason Peck says.

Here are the top contenders in the race to clean up space.

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Swiss Maid

The Swiss CleanSpace One is a tiny space janitor. Roughly the size of a loaf of bread, it will capture an even smaller prey: the SwissCube, a 4 x 4 x 4–in. satellite launched in 2009, which will be defunct by the time CleanSpace One is ready to collect it.

CleanSpace One's designers at EPFL intend to piggyback the device on a commercial satellite launch sometime around 2016. Once in orbit, a small ion engine will propel the little ship. As CleanSpace nears its target, tendrils will unfurl from inside the gadget and, with the help of pressure sensors and artificial muscles, grab onto the SwissCube. Then it will drag the old satellite (which is also owned by EPFL) into the Earth's atmosphere and the two objects will burn up together. CleanSpace One is mostly intended to test the feasibility of the design; EPFL hopes that future models will be able to pull down more than one piece of junk at a time.

Strengths: CleanSpace One uses CubeSat technology, which is a standardized, open-source satellite platform. So if the device is successful, other researchers may be able to build similar designs. A cost of $11 million makes this a steal compared to typical space-exploration missions.

Weaknesses: Aside from the fact that the current design can capture only one satellite, it also can't target very large or very small objects. And it's a one-shot deal: CleanSpace burns up in the atmosphere along with its target. If CleanSpace were to be scaled up and used widely, it would need to be either reusable or cheap enough to launch many devices on these kamikaze missions.

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Laser Broom

The U.S. Air Force first began exploring the laser broom idea in the 1990s. The laser wouldn't try to blow up space junk—that would only create more pieces and exacerbate the problem. Instead, scientists would use the laser to vaporize a tiny bit of the piece of space junk, and the resulting puff of vapor would create enough drag to slow down the target so it would fall into the atmosphere, where the entire thing would burn up.

Strengths: Ground-based lasers avoid launching costs and propellant limitations. Engineer Claude Phipps from the company Photonic Associates, LLC estimates that a medium-powered laser could remove small objects for a few thousand dollars apiece and large objects for $1 million.

Weaknesses: NASA's chief scientist for orbital debris, Nicholas Johnson, says aiming a ground-based laser and hitting a satellite exactly where you want to is no easy feat. "These objects are not nice spheres—they're more like tumbling cornflakes," he says. "They can be very unpredictable." If the laser accidentally hit the wrong object, such as, say, a Chinese satellite, it could spark an international incident. If it hit the right target but in the wrong place, it's possible that the laser accidentally could give the debris more energy and push it into a higher orbit.

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Whoosh It Away

The Space Debris Elimination (SpaDE) system is still in the concept-design stage. Its developer, Raytheon BBN Technologies, has NASA funding to design a system that can fire targeted air puffs into the paths of unsuspecting space trash, increasing drag and forcing the junk to de-orbit. The researchers are considering using air field blasts, explosions, or similar techniques to generate the air puffs. The amount of debris that one device could eliminate would depend on the density of the junk. "The air pulse creates a cloud that impacts any piece of debris that flies through while the cloud is still coherent," Dan Gregory of Raytheon BBN says. "In other words, it depends on how much debris flies through the cloud you create while that cloud is still in tact." Cost is still TBD.

Strengths: The air pulses fall back into the atmosphere, so the device leaves no residue behind and has a minimal impact on the space environment.

Weaknesses: May not be strong enough to take down large objects.

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Tethers

The ElectroDynamic Debris Eliminator (EDDE), created by Star, Inc., captures space junk in a net the size of a house. Other companies have tried to build nets, but what makes EDDE different is that its life span isn't limited by the size of its fuel tank. That's because this junk capturer is powered not by liquid fuel, but by a long conducting wire that generates electricity as it moves through the Earth's magnetic fields. So an EDDE vehicle could operate indefinitely: It could target a piece of debris, capture it in a net, deliver it into the Earth's atmosphere, and then turn around and start over again.

Some parts of the EDDE design, including its kilometer-long tether, will be tested in a Navy-funded trial beginning in September 2013.

Strengths: On average, it takes 10 days to remove an object, so each EDDE vehicle could remove 36 objects per year. At that rate, within seven years 12 EDDE vehicles could remove all 2465 large objects that currently orbit below a 2000-km altitude. And it's relatively cheap, at $5 to $10 million per vehicle.

Weaknesses: It is not economical for EDDE to go after smaller objects. In addition, the electrodynamic wire has broken in previous tethered spacecraft. To avoid that problem, EDDE will use a 1.2-inch-wide reinforced tape.

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Sail Away

Solar sails are one candidate for a future spacecraft-propulsion system. These large sheets capture the physical pressure of sunlight the way that naval sails capture the pressure of the wind. However, NASA scientists are exploring the idea that solar sails could act as parachutes, too and could be a way to pull space junk from orbit.

A vehicle could fly around space, attaching solar sails to pieces of debris. Once attached, the solar sail (which can have surface areas of 300 square feet or more) would unfurl, creating extra drag that would slow the junk's motion and cause it to fall into the Earth's atmosphere. Last spring, NASA tested the NanoSail-D, its first solar sail, and successfully demonstrated its de-orbiting capabilities.

Strengths: NASA could pull many pieces of space junk from orbit and use relatively little propellant.

Weaknesses: Ideally, when space junk reenters the atmosphere it would burn up over an ocean, where falling debris can't injure anyone. But with solar sails, it would be difficult to control where the junk lands.

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